The cost C of running a ship on a certain voyage is said to be given by c=av+b/v where v is the average speed in km/h and a,b are constant.find the value of v in terms of a and b to give the maximum cost,and also find the cost???

Answer 1

c = av + b/v
cv = av^2 + b
av^2 - cv + b = 0
now just use the quadratic formula to find v.

There will only be a maximum cost if a<0, since then the parabola will open downward.